Electric discharge tube



ELECTRIC DISCHARGE TUBE Filed Aug. 4, 1948 WlLLEM 31X PIETERWILLEMYHAAYMAH INVE NTORS AGENT Patented July 18, 1950 PATENT: orriesELECTRIC DISCHARGE TUBE Willem Six and Pieter Willem Haayman, Eind-.hoven, Netherlands, assignors to Hartford National Bank andTrustGompany, Hartford,

Conn, as trustee Application August 4, 1948', Serial No. 42,478 h In theNetherlands August 16, 1947 5 Claims.

Thisinvention relates to an electric discharge tube having .angelectrodesystem which comprises an electrode consisting of a material having ahigh negative temperature coefficient, and to a circuit arrangementcomprising such a tube. v In electro-engineering switches and relays areusedfor-very diverse purposes. The constructions are'suchas to fulfill 1their function best for each different purpose. A common condition whichis nearlyalways imposed is that the relay or the switch should open andclose rapidly and with the use of as little energy as possible, in otherwords little control energy. In mechanical constructions greatachievements have been made but, naturally, a limit is set both to therate of opening and closing and to the energy required. A means whichhas been resorted to for reducing the energy requiredin opening andclosing and for speedingup these operations consists in the constructionof relays andswitches on electronic lines. Thus, for instance, it isknown to use defiection tubes to thisend. In such a tube the electroncurrent is adapted to b controlled very rapidly and with little energy.A disadvantage is, however, that-the current travels by way of theelectron beam. The resistance thus introduced into the electric circuitis high, which may sometimes be very objectionable, for instance if sucha tube should pass speech currents in a telephone circuit. Anotherdisadvantage, which is at least as serious, consists in that such a tubepasses current only in one direction.

In electric discharge tubes it is furthermore known to direct anelectron current on to amat'er'ial having a negative temperaturcoeflicient.

This material is heated by the electron current striking it, due towhich its resistance decreases. Since the material comprises twoelectrodes, it is possible in this manner to cause a current to flowbetween these two electrodes through the material having a negativetemperature coeflicient. In this event "the relay is, for instance,controlled by means of a control-grid surrounding the cathode whichemits the electron current. This yields, as it were a normaltriode-construction, wherein the anode consists of the material having anegative temperature coefiicient. As a material for this anode cuprousoxide has been proposed.

On of the disadvantages from which this known relay tube suffers is thatthe time elapsing before switching the current on is still veryconsiderable, since the anode has a high thermal inertia. This might beavoided byusing a high energy, but in this event special steps must betaken to carry ofi this energy in a short time,

and these steps, in turn, require tosupply more energy, and so on.Finally a limitis set tothe energy per sq. cm. which the cathode iscapable of delivering. In. addition th 'directradiation of heat from thecathode tends to become disadvantageous since this entails an increasein anode temperature.

The present invention meets these drawbacks by providing a bodyconsisting of materials have ing a negative temperature coefiicient,which body comprises at least two conductors, in come bination with anelectron current which is formed into a beam in such manner that onstriking the body having a negative temperature coeflicient it increasesthe conductivity of this body at least a thousandfold in 5 seconds atthe most.

In this manner an electric discharge tube resembling a cathode beam tubeis obtained. However, the electrode finally struck by the electroncurrent is not a luminescent screen or metal elec-' trode but a materialhaving a negative temperature coefficient.

Naturally, the operation of the tube is materially improved with the useof a material having a very high negative temperature coefiicient;

Such materials are, for instance, cobalt oxide with lithium oxide, andzinc titanate or magnesium chromite with magnetite and manganese oxide(M11804) with nickel oxide.

As is known, electric discharge tubes, wherein the electron current isformed into a beam, are adapted to be controlled with comparativelylittle energy.

It is possible to control a tube according'to th invention by means ofdeflection in which, consequently, the beam, in accordance with thedeflection voltage, is either directed or not directed on to the bodyconsisting of a material having a negative temperature coefficient.'Alternatively, however, the beam may either or not be suppressed, forinstance by means of a'grid or a socalled Wehnelt-cylinderto whichanegative voltage may be applied.

Furthermore it is possible to introduce into a single discharge tube aplurality of bodies having a negative temperature coeflicient and todirect the beam by deflection now to one body now on the other. Such atube may advantageously be used in a circuit-arrangement for automatictelephone exchanges, wherein it is adapted to replace mechanical relaysor selectors.

In a particular form of construction of a tube according to theinvention the electron current is continuously directed to the body madefrom a material having a negative temperature coefiicient, but is notexclusively concentrated thereon. In this manner the body iscontinuously heated, it is true, but the value both of the intensity ofthe electron current and of the size of the body are such that thisheating does practically not involve any conductivity. By applyingadefinite control voltage to a concentrating electrode provided in thetube, the beam is adapted to be concentrated on the body so that thelatter is strongly heated. and becomes conductive.

To gain an idea of the size of the body having a negative temperaturecoefiicient, and of the required energy and the results obtained, thefollowing example is given.

In a cathode-beam tube permitting 0.2 watt to be directed on to the bodyhaving: a' negative temperature coeflicient, this body had a volume of0.07 cu. mm. This body consisted of cobalt oxides with lithium oxide. Bymeans of 0.2 watt this'body could be heated to 300 C. in one secondwhich resulted. in increasing its conductivity 10,000 times.-v

Bod'y' consisting of zinctitanate with magnetite or of "manganese oxide.andnickel. oxide would require avolume of 0.1 cu. mm.

In order that the invention may be clearly understood and. readilycarried into efiect it will now be explained more fully with referenceto the accompanying drawing, given by Way of example.

Fig. 1 represents diagrammatically an electric discharge tube accordingto the invention, in which the electron current formed into a beam isadapted to be directed, by means of: deflection electrodes, on to threebodies provided in the tube which bodies consist of a material having anegative temperature coefficient.

Figures 2 and 3 represent forms of the body having a negativetemperature coefiicient.

In Fig; 1 the wall of the discharge tube is designated l. Th referencenumeral 2 denotes'the cathode. The system by means of whichthe'concentrated beam is obtained is represented. diagrammatically anddesignated 3. The deflection electrodes are designed 4 and 5'. Thereference numeral 6 denotes the bodies which have a negative temperaturecoefficient and each of which is clamped between two electrodes 1 and 8.In accordance with the voltage onthe deflection electrodes 4'. and5,.the beam strikes one of the bodies 6'. In this event the heating ofthese bodies causes the passage of a, current between electrodeslandrfl'. These electrodes are naturally connected'to a circuitcomprising a source of current.

InFig. 2 the body having negative temperature coefficient consists. oftwo concentric conductors 9 and In between which the material: ll havinga negative temperature coefficient is sandwiched. This body may forinstance, beobtained by. drawing out a corresponding body of largersizeto the desired size.

Fig. 3 represents a body which is indirectly heated. In this figure thematerial having a negative temperature coeflicient is designated l2 andthe electrodes between which the current passes bear the referencenumerals l3 and I4. The material l2 having a negative temperaturecoefficient is externally provided with a conductive coating I5 whichmay be connected to the positive end of a, source of potential, of whichthe negative. end is connected to the cathode of the discharge tube.

What We. claim is:-

1.- An electron discharge device comprising an envelope, a cathodesource of a beam of electrons within said envelope, means to concentratesaid electrons-into a beam of given energy content, means to controlsaid concentrated electron beam, a pair of electrodes positioned in saidenvelope and spaced from said cathode, said concentration means and saidcontrol means, and a mass of an electrically conductive material havinga negative temperature coeflicient' supported between and electricallyconnected to said pair of electrodes, said control means being adaptedto direct said electron beam to said mass, said mass having a thermalinertia at which impingement of said beam of given energy contentthereon producesa thousandfold increase in the conductivity thereof'inapproximately- 5 seconds.

2. An electric discharge device as claimed in claim 1, characterisedin-that the material having negative temperature coefiicient' consistsof cobalt oxide With lithium oxide.

3. An electric discharge device as claimed in claim 1, characterisedin-that'the materialhaving a negative temperature coefiicient consistsof Zinc titanate with magnetite. Y

4'. An electric dischargedevice as claimed in claim 1 characterised inthat thematerial having a negative temperature" coefficient consists ofmanganese oxide with nickel oxide.

5. Anelectric disch'argeide'vice as claimed" in claim 1, characterisedin that the discharge device'comp'rises a plurality of bodies havinganegativetemperature coeflicient' onto which'th'e beam may be directedby means of deflection control.

WILLEM- SIX. PIETER WILLEM I-IAAYMAN'.

REFERENCES. CITED The following referencesare of recordin the file ofthis patent:

UNITED STATES PATENTS Number Namev Date 2,237,671 Kallmann Apr. 8, 19412,357,922 Ziebolz et al. Sept. 12,.1944 2,314,666 Cunnifi". May 1, 1945

